I would try to send a photo to Ruger. Most likely the increased height is causing it to shoot low.

 

You might try shooting from bench rest to verify you are not pulling down off aim point as you squeeze the trigger.
Also you might shoot a few targets at different distances and measure how low it is shooting at different distances.
This info may help point to the cause.

 

I checked both of my S-380's and they also have a small gap between the bottom of the site and the top of the slide. I do not have issues with them shooting low.

 

Two very important questions: How low is it? And how far away is the target?

Remember that the muzzle is lower than the front sight, so it takes some distance for the bullet to rise enough to intersect with the line of sight.

 

I think it is important to note that a bullet does not physically rise after it leaves the barrel. But the distance to target is important in any analysis because the line of sight from a sight higher than the barrel will make it seem like it rises. What is actually happening is that the line of sight will be different based upon distance to target. So the closer to target the more the bullet will appear to be low.

Solution: When shooting a pistol at close distance and perceiving low shooting based upon POA to POI the correction is to aim a bit higher that the point you wish to hit. That adjusts the point at which the bullet intersects the line of sight.

 

From your picture I wouldn't say that was "normal". Not on any pistol I own anyway.

 

The Hi-Viz sight I put on my Sec9c looks like that.

It does not shoot low for me.

My only Ruger that does “shoot low” is my LCP Max.

 

But therein lies the rub. A sight you put on, not the factory. Not to be critical. Just sayin'💥🔫